Cross Country Magazine Tuesday Tip

This week's tip comes from the classic textbook Understanding the Sky

Lift in a Thermal

Once an ideal thermal organises itself it ideally takes on the shape of a mushroom turning itself inside out, like a smoke ring.

The air rising in the core or centre of the thermal is moving upward about twice the rate of the top of the thermal. Thus it is possible to be near the top and climbing slowly while other pilots are climbing up to you from below.

It is not always their better thermalling skills at work in this situation, but their position in the faster rising air.

As the thermal rises it pushes the air above it up and out of the way, creating sink and turbulence along the sides of the thermal.

An area of turbulent mixing occurs at the leading edge of the thermal. This sink and turbulent air are often what announces the thermal to a searching pilot.

Blue Skies!

Cross Country Magazine Team

Lift in a Thermal

Stop the main glider from flying and pull it in Understanding the Sky is available at
PS. Last week's Tuesday Tip 'How to throw a reserve' raised the odd eyebrow. When we wrote, "Stand up and get out of the harness…" we did not mean literally to unclip and get out of the harness. We meant, "Sit up in the harness and prepare to make a parachute landing roll". Please, whatever you do after throwing your reserve, do not unclip: do not get out of your harness until you are safely on the ground. Thank you.